<!DOCTYPE html>
<html>

	<head>
		<meta charset="utf-8" />
		<title>计算器</title>
	</head>

	<body>
		<h1 align="center">计算器</h1>
		<style type="text/css">
			table{
				margin: auto;
			}
			table td {
				width: 500px;
				height: 80px;
				}		
							
		</style>

		<table width="500px" height="400px" border="1" bgcolor="deepskyblue"
			style="text-align:center ">
			
			<tr>
				<td colspan="4">请输入：</td>							
			</tr>

			<tr>
				<td>+</td>
				<td>—</td>
				<td>×</td>
				<td>÷</td>				
			</tr>

			<tr>
				<td>%</td>
				<td>7</td>
				<td>8</td>
				<td>9</td>				
			</tr>

			<tr>				
				<td>√</td>
				<td>4</td>
				<td>5</td>
				<td>6</td>				
			</tr>

			<tr>
				<td>←</td>
				<td>1</td>
				<td>2</td>
				<td>3</td>				
			</tr>

			<tr>
				<td>清除</td>
				<td>0</td>
				<td>.</td>
				<td>=</td>				
			</tr>

		</table>

	</body>

</html>